1. Field of the Invention
The present invention relates to bend detector used to map out a pipeline system conveying materials such as oil, natural gas, water and the like. More particularly, the present invention relates to a bend detection apparatus used in conjunction with a pipeline pig assembly.
2. Prior Art
When pipeline systems are laid, most of the necessary bends are provided by manufactured or standard pipe elbows. Slight bends or elbows are usually generated while the pipeline is being laid. However, older pipeline systems generally do not have alignment sheets showing the locations of the standard elbows. On the newer pipeline systems, any repairs that have been made may render a current alignment sheet either incomplete or inaccurate. Precise location of any sharp bend is necessary before various maintenance operations, such as the use of corrosion tools, can be initiated.
There are three general types of standard bends or elbows commonly used for pipeline systems. The sharpest bend is a 90.degree. 11/2 radius bend, wherein the pipe curves 90.degree. along an arc whose radius is 11/2 times the diameter of the pipe. The other two bends are a 90.degree. 3 radius bend and a 45.degree. 11/2 radius bend. More shallow bends can be made on site during the laying of the pipeline.
Pipeline caliper pigs used to inspect pipeline systems are well known. These pipeline pigs are used to detect ovality, serious dents and the like within the interior surface of the pipeline. However, some pipeline pigs and various curvature sensing apparatus are unable to negotiate the sharp bends of factory elbows.
A preliminary search was conducted and the following prior art patents were uncovered:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 3,496,644 Short Feb. 27, 1970 3,718,9781 Van Koevering et al. March 6, 1973 3,755,908 Ver Nooy Sept. 4, 1973 3,780,442 Gresho Dec. 25, 1973 3,789,511 Groom et al. Feb. 5, 1974 3,821,856 Rapp July 2, 1974 3,882,606 Kaenal et al. May 13, 1975 3,886,665 Lowen June 3, 1975 ______________________________________
A pipeline survey vehicle is disclosed in the patent to Van Koevering et al. A motor propelled vehicle is inserted into a pipeline for sensing deflection in a vertical plane. The Van Koevering vehicle is an essentially bullet-like sled with a gravity operated steering means. A bend is detected by means of a plurality of gauge elements which come into contact with the interior surface of the pipeline.
A standard pipeline caliper pig is disclosed in U.S. Pat. No. 3,755,908 to Ver Nooy. The caliper pig is inserted into a pipeline to locate deviations along the interior of the pipe such as dents, ovality and the like.
U.S. Pat. No. 3,789,511 to Groom et al., an apparatus for sensing a curvature in a conduit is disclosed. The Groom patent is used to determine the curvature and strain of a pipeline as it is being laid on marine bottoms. This apparatus comprises a pair of pivotally interconnected rigid components which are subsequently connected to a traction unit which pulls the apparatus through the conduit. Strain gauges are used in conjunction with a rod which passes through the pivotal interconnection to determine the curvature of the pipeline.
A method and apparatus for measuring curvature and variations in pipelines is disclosed in U.S. Pat. No. 3,882,606 to Kaenel et al. The Kaenel apparatus comprises an instrumented pig carrying an array of sensing wheels. As the pig travels down a length of the pipeline, the rotation of the sensing wheels is encoded as a function of the axial distance traveled.
A monitoring apparatus for measuring the varying radii of curvature along the axis of a bore is disclosed in U.S. Pat. No. 3,886,665 to Lowen. The monitoring apparatus comprises an elongated or tubular body member having a roller assembly mounted at each end. The Lowen apparatus is used for indicating the length of the offset over the chord length.
In light of the above, and as will more fully appear hereinafter, the prior art does not disclose the means for detecting bends in a pipeline in the manner disclosed and claimed in the present invention. No prior art device discloses an apparatus used in conjunction with a pig assembly that is system propelled. No prior art patent discloses a bend detector having a broad range of maneuverability and capable of traversing through abrupt bends without buckling in the pipeline.